1. Field of the Invention
The present invention relates to reactive-power control apparatus that control a static reactive-power compensator in which reactive power is generated to mitigate voltage fluctuations in an electric power system, and to reactive-power compensators that utilize the control apparatus.
2. Description of the Related Art
A reactive power compensator utilizes a capacitor, a reactor, and/or a static reactive-power compensator (also referred to as a static VAr compensator, or “SVC”); these are used according to reactive-power requirement. The capacitor or the reactor (commonly referred to as a “reactive power compensation device”) is connected to an electric utility-network or power-system by way of a switchgear; because an on/off operation time is required for the switchgear, an instantaneous response thereof can not be realized. On the other hand, an SVC generates leading or lagging reactive power by controlling a switch constructed of semiconductor devices; therefore, the reactive power can be instantaneously controlled.
In a conventional reactive-power compensator, a sum total of the reactive power generated by an SVC and that supplied by a reactive power compensation device is controlled so that the total reactive power becomes equal to the amount required to mitigate voltage fluctuation. (For example, refer to Japanese Patent Laid-Open Publication No. H10-268952.)